Segmental motor and sensory innervation of muscles in anterior leg compartment as revealed by retrograde transport of horseradish peroxidase

Horseradish peroxidase (HRP) tracing technique was used to label and localize motor and sensory neurons innervating tibialis anterior, extensor hallucis longus and extensor digitorum longus muscles of the anterior leg compartment of the rat. The tibialis anterior sensory neurons were located in the ipsilateral L4 and L5 spinal ganglia. Cells of origin of tibialis anterior motor endings were also found in the ipsilateral ventral horn of the same cord segments as the labeled sensory ganglia. Extensor hallucis longus sensory neurons were located in L4 to L6 spinal ganglia, while its labeled motor neurons were located in L4 and L5 spinal cord segments. The motor neurons innervating the extensor digitorum longus muscle were located in L4 to L6 spinal cord segments; its sensory neurons were previously localized. All labeled motor and sensory neurons were present on the ipsilateral side. Almost all motoneurons innervating the 3 muscles were present in the dorsolateral nucleus of the ventral horn.